Bosch 2400E Reference manual

Service bulletin
Replacing and cleaning electrodes
TWH-G2-23 | 2400E, 2400EO, 250SX, 250SXO, 635ES, 635ESO
Introduction
The electrode set may need to be cleaned or replaced if the
heater has frequent EC error codes or does not spark.
Tools needed:
Philip head screw driver
8mm open end wrench or small adjustable wrench
Steel wool for cleaning electrodes
Removing electrode set
1. Turn off gas to heater using installer supplied manual shut off
valve.
2. Turn power switch to the off (O) position and unplug heater.
3. Remove cover per chapter 4 in installation manual.
4. Remove brass phillips-head screws to release holding bracket.
Accessing electrode set
Holding
bracket
screws
Air intake
duct
Air intake
duct screws
Holdin
g
b
rac
k
e
t
scre
w
s
A
ir inta
k
e
duct
A
ir in
ta
k
e
d
uct screw
s
5. Remove air intake duct: remove two philips-head screws on the
bottom of the air intake duct and then pull forward.
NOTE: There is a thin black oring between the air intake duct and
the gas/air mixer that may fall out.
6. Disconnect three yellow wires connected to the bottom of the
electrode set.
7. Remove two 8mm retaining nuts.
Electrode connectors
8mm retain-
ing nuts
Ignitor rods
connectors
Flame sensor
rod connector
8
mm r
et
tai
n-
t
i
ng nut
s
I
g
nitor rods
co
nn
ect
o
r
s
Fl
a
m
e
se
e
n
sor
e
ro
d
con
n
n
ector
n
8. Lower the electrode set slowly and rotate inward to remove.

Data subject to change without notice | Printed in the USA | 01.2007 Bosch Water Heating
BBT North America Corporation
Bosch Group
Bosch Water Heating
340 Mad River Park
Waitseld, VT 05673
Telephone [phone]
Fax [phone]
[email protected]
Cleaning electrode set
1. If electrode set gasket is discolored or torn, replace with a new
gasket.
2. Using steel wool, gently polish all surfaces of the ame sensor
rod and electrodes.
Electrode set
Electrode gasket
Electrodes
Flame sensor
8mm retaining nuts
Replacing electrode set
1. Gently place new gasket on studs. The studs will hold the gasket
in place.
2. Carefully feed tips of electrode set into bottom of burner bed
and rotate out while inserting.
3. Ensure proper seal between bottom of burner bed and the
electrode set.
4. Replace the two 8mm retaining nuts.
5. Connect the two similar yellow wires to the left and center
terminals (ignitor rods). Connect the thinner yellow wire to the
right terminal (Flame sensor). Ensure the connectors t snugly
on the terminals.
6. Place thin black o-ring around the outside lip of the gas/air
mixer.
7. Push air intake duct in place with two hands and hold. Ensure
the top of the air intake duct is level and the back rubber gasket
is tucked under the bed.
8. Replace two phillips-head screws on the bottom of the air intake
duct.
9. Replace holding bracket and cover.
10. Plug unit in and turn power switch to on (I) position. Reset any
error that is displayed.
11. Open manual gas shut off valve.
12. Return to service.
Service bulletin
2 | TWH-G2-23 | 2400E, 2400EO, 250SX, 250SXO, 635ES, 635ESO